Gentlemen
This thread has really come to life in the last couple of days with some extremely interesting points being made, but also some which I feel could be misleading to owners looking for rigs for their boats. I want to ‘wade in’ with a long examination but life is just too hectic at the moment, but now at 5 AM in the morning I find that thinking about it is stopping me getting the sleep I need.
Paul, your point that it is important to consider the hull before considering the rig is a strong one, but I feel there is a risk that we could end up suggesting that one particular type of hull should only have a particular type of rig mounted on top, and so on down the line. This is not something we should encourage as it could discourage experimentation, and could discourage the use of some very seaworthy hulls.
Take the analogy of internal combustion engines. It would be ridiculous to fit a high revving F1 racing car engine to a cement/ concrete mixer, or the put a single cylinder diesel thumper in a F1 car, but there is no reason why these engines will not do jobs other than the ones they were basically designed for. A cement mixer does not require 300 bhp at 18,000 rpm, but if properly scaled and fitted with an appropriate gearbox the same engine could drive a very long line of cement mixers. The big difference in the two engines is in their efficiency in both power/ torque per calorie fuel intake and power to weight ratio. Think of using an Olympus jet engine, as used in the supersonic Concorde or Phantom fighter, in a naval destroyer and the answer is that the power plant can be used efficiently in quite different applications by adapting it's output to the different vehicle/ vessel.
Similarly, different boat hulls have different sailing characteristics in terms of keel efficiency and wave making drag. All hulls deserve an efficient rig and to put an inefficient rig on either a ‘blunt tub’ or a sleek racing hull is pointless, or at least a waste of effort. The important thing, as you suggest Paul, it to match the rig to the hull. Rather than fit a stereotype rig I believe it is more important to match the area of the rig so that the hull is not over pressed or under driven.
I had a most interesting sail on Anthony Cooke’s dinghy ‘Duffy’ in the summer in the restricted waters of the river Yar above the bridge at Yarmouth IOW. There was no more than 5 boat lengths available when beating before having to start the next tack. Now this is a situation in which the split junk is ideal yet progress was slow. The dinghy has a long straght keel which ends in a long stemmed wine glass shaped transom, and a rudder only a little deeper than the stem of the wine glass. The relatively small metal plate centreboard was not that effective, so the hull was happy to run in a straight line when travelling at a reasonable speed, but when slowed down even slightly the leeway was horrendous, the hull drag rocketed up and the hull slowed right down. Apparently the local sailmaker was very complementary about the performance of the split rig, probably because he knew the shape of the hull and was aware that even with a Bermudan rig it would have been very difficult to drive up wind in a narrow river.
Now I am convinced that if fitted with a flat junk sail that particular hull would not be able to sail up wind at all in the narrow waters of the river as I doubt if it would be able to get through the wind even once, and even if motored or rowed onto the correct heading would not drive fast enough to make the keel work and reduce the hull drag.
My point is that every hull, be it a blunt or fast shape with a good keel, will benefit from a rig with a high lift/ drag ratio, or in other words, an efficient rig. A well designed cambered rig can give high lift, and should also give good alpha tolerance to the varying wind direction due to wave action. Equally, a well shaped sail profile should produce a low drag result, remembering that total rig drag is made up a number of components. Flat rigs are just not able to produce a high L/D ratio so are not able not produce the best performance possible from any hull.
I can hear the long distance cruising brigade reaching for their keyboards, but please remember that I am talking aerodynamics and not structural considerations. If you are cruising and have a rig that will tack positively through 80° that it is not necessary to sail it that way when plodding to windward. It is useful to get you out of a sticky situation, but to cruise at 50° to the wind will be more comfortable and probably more upright even than the flat sail for the same or better hull speed. Similarly, when further off the wind the overall speed should be either higher, if wanted, or the same if reefed further and producing less sideways stress on the boat. If the wind is light then the greater performance from the available sail area on all points of sail should be welcome to any cruising sailor.
When cambered rigs are criticised in terms of chafe and cruising durability then we should look for passive ways to overcome these problems, if they actually are problems and not over talked excuses to make a ‘political’ point.
You may notice that I mentioned that I was talking about ‘well designed’ cambered junk rigs. Reading some of the recent reports which have compared flat to cambered rigs I realise that there is a wide range of performance being achieved from some of the cambered rigs being built both by amateurs and professional sail makers. Similarly the droopy appearance varies from rig to rig. The various methods of producing cambered panels are not all equal, and more thought should be put into this area. Somewhere along the line we must encourage the building of ‘good’ cambered sails and not just any old ‘cambered’ sail. Then opinions may change as sailors experience good cambered rigs.
Having got that off my chest there is now no point in going back to bed. Once again I have lost sleep over junk rigs. That’s not good.
Cheers
Slieve
PS. I have just heard on the Breakfast Programme on TV that one of the world’s longest running comics, the ‘Dandy’ will be printing its last copy today. From now on it will only be published on-line. Is this a sign of the times for all publications?
PPS. I tried an idea sent by Arne to help me paste this .doc into the thread, but to no avail, and ended up re-typing most of it. There is something very funny going on with this programme, or have I been censored?